Reflective articles and methods for increasing photosynthesis

ABSTRACT

Provided is a reflective article including a first reflecting material and a second retro reflecting material; where sunlight that is photosynthetically active is at least partially reflected by the article and sunlight that is not photosynthetically active is at least partially retro reflected by the article. Also provided is a method for growing a plant, where the method includes placing the reflective article under, around, or in the proximity of the plant.

BACKGROUND

The present technology relates generally to articles and methods forgrowing plants.

Photosynthesis, also called carbon fixation, is the process by whichplants utilize solar energy to synthesize carbohydrates and otherorganic molecules from carbon dioxide and water. Carbohydrates and othermolecules are synthesized, according to the photosynthetic capacity ofthe plant, to meet the needs of the growing plant tissues including thewoody tissue, leaf tissue, developing flower buds and developing fruit.

The effects of enhanced photosynthesis generally include improved cropsand increased yields, e.g., increased fruit size or production (usuallymeasured in weight per hectare or acre), improved color, increasedsoluble solids, e.g., sugar, acidity, etc., and reduced planttemperature.

Conversely, the effects of a depleted or insufficient photosyntheticcapacity generally include diminished crop yields, decreases inproductivity, and “excessive fruit drop.” Normal fruit drop occurs whenthe photosynthetic capacity of the plant is sufficient during thegrowing season to simultaneously support tree growth, fruit development,and the initiation of flower buds. Excessive fruit drop occurs whenphotosynthetically derived carbohydrates become limiting to all thegrowing tissues while fruit is developing. In response, the plant abortsand drops the developing fruit, and limits the initiation of flowerbuds.

Articles and methods are needed to maintain or bolster thephotosynthetic capacity of plants and increase agricultural yields andthe quality of crops. An additional need exists, in view of anincreasing demand for organic produce, for articles and methods thatincrease agricultural yields without treating the plant directly withchemical additives.

SUMMARY

The present technology provides a reflective article for reflectingphotosynthetically active bands of sunlight towards one or more plants,and methods for growing plants where the method includes placing thereflective article under, around or in the proximity of the plants.

According to one aspect, the present technology provides a reflectivearticle including one or more diffuse reflecting materials and one ormore retro reflecting materials; where sunlight that isphotosynthetically active is at least partially diffuse reflected by thearticle and sunlight that is not photosynthetically active is at leastpartially retro reflected by the article. In some embodiments, thearticle is configured for placement under, around, or in the proximityof the plant. In some embodiments, when the article is under, around orin the proximity of a plant, sunlight that is photosynthetically activeis at least partially diffuse reflected towards leaves of a plant by thearticle and sunlight that is not photosynthetically active is at leastpartially retro reflected away from the leaves of the plant by thearticle. As such, at least some of the sunlight that is notphotosynthetically active is retro reflected back towards the sun,whereas at least some of the sunlight that is photosynthetically activeis diffuse reflected towards the plant.

In another aspect, the present technology provides a method for growinga plant, the method including placing a reflective article under, aroundor in the proximity of a plant, wherein the reflective article is asdescribed herein.

The foregoing is a summary and thus by necessity containssimplifications, generalizations and omissions of detail. Consequently,those skilled in the art will appreciate that the summary isillustrative only and is not intended to be in any way limiting. Otheraspects, inventive features, and advantages of the devices and/orprocesses described herein, as defined solely by the claims, will becomeapparent in the detailed description set forth herein and taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein.

FIGS. 1A-1B illustrate, in accordance with an embodiment, a reflectivearticle as described herein, that has been placed under, around or inthe proximity of trees, where relatively intense overhead sunlight thatis photosynthetically active is at least partially diffuse reflected bythe article towards the trees, and relatively intense overhead sunlightthat is not photosynthetically active is highly retro reflected by thearticle away from the trees.

FIGS. 2A-2B illustrate, in accordance with an embodiment, a reflectivearticle as described herein, that has been placed under, around or inthe proximity of trees. Relatively mild non-overhead sunlight that isphotosynthetically active is at least partially diffuse reflected by thearticle towards the trees, and relatively mild non-overhead sunlightthat is not photosynthetically active is minimally retro reflected bythe article away from the trees.

FIG. 2C illustrates, in accordance with an embodiment, a reflectivearticle as described herein, that has been placed as a ground coverunder, around or in the proximity of trees, where the ground coverdecreases the thermal emissivity of the ground that it covers.

FIG. 3 illustrates, in accordance with one embodiment, a method forgrowing a plant, the method including placing a reflective articlebeside or beneath the plant, wherein the reflective article is asdescribed herein.

FIG. 4A illustrates, in accordance with one embodiment, aretro-reflector based on a corner cube element.

FIG. 4B illustrates, in accordance with one embodiment, aretro-reflector having refracting optical elements with a reflectivesurface as described herein.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here.

Referring to FIGS. 1A-1B, in accordance with one embodiment, anillustration is provided of a reflective article 10, as describedherein, that has been placed around and beneath trees 12. In accordancewith one embodiment, the sun 14 in FIGS. 1A-1B is directly over thetrees 12 as it would be at approximately noon, the sunlight in FIGS.1A-1B is relatively intense, substantially all of the sunlight that isphotosynthetically active 16 is diffuse reflected by the diffusereflecting material 20 of article 10 towards the leaves of the trees 12,and substantially all of the sunlight that is not photosyntheticallyactive 18 is retro reflected by the retro reflecting material 22 ofarticle 10 away from the leaves of the trees 12. Partition 29, shown asa dashed line, is optional. Thus, the reflective article can be one ormore layers. Corner-cubes 24 retro-reflect photosynthetically inactivelight 18. Particles 26 and 28 optionally include diffuse reflectingmaterials, such as a metamaterial, liquid crystal, photochromicmaterial, thermochromic material, or a combination thereof, whichdiffuse reflect photosynthetically active light 16.

Referring to FIGS. 2A-2B, in accordance with one embodiment, anillustration is provided of a reflective article 10, as describedherein, that has been placed around and beneath trees 12. In accordancewith one embodiment, the sun 14 in FIGS. 1A-1B is not directly over thetrees 12 as would be so in the morning or late afternoon, the sunlightin FIGS. 2A-2B is relatively mild, substantially all of the sunlightthat is photosynthetically active 16 is diffuse reflected by the diffusereflecting material 20 of article 10 towards the leaves of the trees 12,some of the sunlight that is not photosynthetically active 18 is retroreflected by the retro reflecting material 22 of article 10 away fromthe leaves of the trees 12, and some of the relatively mild sunlightthat is not photosynthetically active 18 is diffuse reflected by retroreflecting material 22 of article 10 towards the leaves of the trees 12.Partition 29, shown as a dashed line, is optional. Thus, the reflectivearticle can be one or more layers. Corner-cubes 24 retro-reflectphotosynthetically inactive light 18. Particles 26 and 28 optionallyinclude diffuse reflecting materials such as a metamaterial, liquidcrystal, photochromic material, thermochromic material or a combinationthereof, which diffuse reflect photosynthetically active light 16.

Referring to FIG. 2C, in accordance with one embodiment, an illustrationis provided of a reflective article 10 that has been placed as a groundcover around trees 12, where the ground cover decreases the thermalemissivity 42 of the ground that it covers and retains temperature inthe ground and roots 44 of the trees 12.

Referring to FIG. 3, a flowchart depicts a process 30 for growing aplant and using a reflective article, as described herein, to decreasethe amount of water that is consumed by a plant. A reflective article isfirst placed beside or beneath a plant as described herein (step 32).According to one embodiment, a base measurement is taken of the amountof water that is consumed by the plant (step 34). The efficiency isincreased with which the article retro reflects sunlight (that is notphotosynthetically active) away from the plant if the amount of waterthat is consumed by the plant has not decreased (step 36). Theefficiency is maintained with which the article retro reflects sunlight(that is not photosynthetically active) away from the plant if theamount of water that is consumed by the plant has decreased (step 38).

Referring to FIG. 4A, a retro-reflector based on a corner cube elementis shown.

Referring to FIG. 4B, a retro-reflector having refracting opticalelements with a reflective surface is shown.

The technology is described herein using several definitions, as setforth throughout the specification.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the elements (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext.

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “about” will mean up to plus or minus 10% of the particular term.

In some embodiments, the light may be sunlight or artificial light.

The present technology relates generally to reflective layers andreflective materials for increasing photosynthesis in plants capable ofphotosynthetic activity. As used herein, the term plant refers to anorganism capable of synthesizing complex organic material utilizing, butnot limited to, carbon dioxide, water, inorganic salts, and light energycaptured by light-absorbing pigments, such as but not limited tochlorophyll and other accessory pigments. Plants are photoautotrophs andare able to create their own food directly from inorganic compoundsusing light energy.

In some embodiments, the photosynthetic process consists of lightreactions and dark reactions, whereby carbon dioxide (CO₂), water (H₂O),and light energy are used to synthesize an energy-rich carbohydrate. Ina general case, the carbohydrate produced is glucose (C₆H₁₂O₆), with anoxygen by-product.

Pigments are chemical compounds which reflect only certain wavelengthsof visible light. Pigments can reflect light and can absorb certainwavelengths. The ability to absorb only certain wavelengths of light isuseful to plants and other autotrophs that make their food usingphotosynthesis. Plants, algae, and cyanobacteria use pigments as themeans by which the light energy is captured for photosynthesis. Eachpigment reacts with a specific narrow range of the electromagneticspectrum; thus, a photosynthetic organism may produce several differentpigments in order to increase its light energy capture.

As used herein, the term “chlorophyll” is used to describe a biomoleculethat is critical in photosynthesis, and which allows organisms to absorbenergy from light. Chlorophyll absorbs light most strongly in the blueportion, and to a lesser degree, in the red portion of theelectromagnetic spectrum. The green color of chlorophyll is due to thebiomolecule's poor absorption of green and near-green light. Chlorophyllis structurally similar and produced through the same metabolic pathwayas other porphyrin pigments such as heme, an iron compound ofprotoporphyrin constituting the pigmental or protein-free part of thehemoglobin molecule, responsible for the molecule's oxygen-carryingproperties. The most widely distributed form that occurs in terrestrialplants is chlorophyll a.

Table 1 lists representative chlorophyll structures.

TABLE 1 Chlorophyll a Chlorophyll b Chlorophyll c1 Chlorophyll c2Chlorophyll d Chlorophyll f Mol. C₅₅H₇₂O₅N₄Mg C₅₅H₇₀O₆N₄Mg C₃₅H₃₀O₅N₄MgC₃₅H₂₈O₅N₄Mg C₅₄H₇₀O₆N₄Mg C₅₅H₇₀O₆N₄Mg Formula C2 group —CH₃ —CH₃ —CH₃—CH₃ —CH₃ —CHO C3 group —CH═CH₂ —CH═CH₂ —CH═CH₂ —CH═CH₂ —CHO —CH═CH₂ C7group —CH₃ —CHO —CH₃ —CH₃ —CH₃ —CH₃ C8 group —CH₂CH₃ —CH₂CH₃ —CH₂CH₃—CH═CH₂ —CH₂CH₃ —CH₂CH₃ C17 group CH₂CH₂COO- CH₂CH₂COO- CH═CHCOOHCH═CHCOOH CH₂CH₂CO CH₂CH₂COO- Phytyl Phytyl Phytyl C17-C18 Single SingleDouble Double Single Single bond (chlorin) (chlorin) (porphyrin)(porphyrin) (chlorin) (chlorin) Occurrence Universal Mostly VariousVarious Cyano Cyano plants algae algae bacteria bacteria

As used herein, photosynthesis frequently occurs in plastids within thephotosynthetic organism, such as chloroplasts in plants. Plastids aremembrane-bound organelles containing photosynthetic pigments such aschlorophyll, situated within an organism's cells.

As used herein, the term “plant” refers to any green plant havingchloroplasts for photosynthetic reactions.

In some embodiments, the plant includes fruiting, agricultural, andornamental crops and the products thereof, including those selected fromthe group consisting of fruits, vegetables, trees, shrubs, flowers,grasses, roots, seeds, landscape plants, ornamental plants, agriculturalplants and adornments and floriculture such as roses.

Plants as described herein may be collected and processed into afeedstuff (i.e., any edible substance that is ingestible by any animalsuch as grains, fruits, flowers, tubers, roots, vegetables, proteins,leaves, grasses etc.) or feedstock (i.e., any chemical or polymerfeedstock used for industrial purposes such as hydrocarbons, sugars,alcohols, peptides, proteins, natural rubber, synthetics, bioethanol,biodiesel, biomass) or non-food crops used in a natural state (i.e., anynon-food crop used for use as fuel, furniture, jewelry, perfumes,ornamental plants, or floriculture).

The plants described herein include agricultural plants of which a partor all is harvested or cultivated on a commercial scale or which serveas an important source of a feedstuff or feedstock as described above,fibers (e.g., cotton, linen), combustibles (e.g., wood) or otherchemical compounds. Agricultural plants also encompass horticulturalplants, i.e., plants that are grown in gardens (and not in fields), suchas certain fruits and vegetables. Agricultural plants further includefloriculture plants such as flowering plants, household plants,ornamental plants, or any such adornment-producing plant.

Examples of agricultural plants that are used as feedstuff or feedstockinclude soybean, corn (maize), wheat, triticale, barley, oats, rye,rape, such as canola/oilseed rape, millet (sorghum), rice, sunflower,cotton, sugar beets, pome fruit including apples, pears and quince,citrus, bananas, strawberries, blueberries, almonds, grapes, mango,papaya, peanuts, potatoes, tomatoes, peppers, cucurbits, cucumbers,melons, watermelons, garlic, onions, carrots, cabbage, beans, peas,lentils, alfalfa, trefoil, clovers, flax, herbs, grasses, lettuce, sugarcane, tea, tobacco and coffee.

Most photosynthetic organisms are plants. Plants are defined to be greenplants (Viridiplantae in Latin), organisms belonging to the kingdom,Plantae. Multicellular groups such as flowering plants, conifers, fernsand mosses, and, depending on the definition, green algae, are includedin Viridiplantae. Fruits, vegetables, and grains are considered to beplants.

Green plants have cell walls that include cellulose, andcharacteristically receive most of their energy from light viaphotosynthesis, utilizing chlorophyll which is contained in chloroplastsand gives them a green color. In some cases, plants that cannot producenormal amounts of chlorophyll or photosynthesize may be parasitic.

In some embodiments, the plant is grown on a farm, orchard, in a forest.In some embodiments, the plant produces a grain, fruit, vegetable,feedstuff, or feedstock. In some embodiments, the plant producessoybean, corn, wheat, barley, oats, rye, rape, millet, rice, sunflower,cotton, sugar beets, bananas, strawberries, blueberries, grapes,peanuts, potatoes, tomatoes, peppers, cucurbits, cucumbers, melons,watermelons, garlic, onions, carrots, cabbage, beans, peas, lentils,alfalfa, trefoil, clovers, flax, herb, grass, lettuce, sugar cane, tea,tobacco, or an adornment or floriculture, such as flowering plants,household plants, ornamental plants, or any such adornment-producingplant, including plants used in the production of flavorings, incense,fragrances and perfumes.

In some embodiments, the plant is a tree. Such trees include thoseproduced for floriculture and ornamentation, for reforestation, forfuels, for soaps, perfume, furniture, and for feedstuff and feedstock.Examples of trees used for fuel include poplar, oak, pine andeucalyptus. Examples of trees used for their flower petals, leaves,bark, wood, seeds, roots, fruit rind, gums, and resins includesandalwood and ylang-ylang. Examples of trees used for reforestation,furniture and building materials include oak, pine and redwood. Examplesof trees used for their fruits are citrus, pome fruit including apples,pears and quince, stone fruit such as peaches, mango, lychee, longan,mango, avocado, almonds, and macadamia nut. Examples of other treesgrown for their fruit are coffee and papaya.

As used herein, the term “under a plant” or “placement under a plant” orin the “vicinity” of the plant, or “around a plant”, or in the“proximity” of a plant refers to any distance between a plant and thearticles described herein that can be traversed by photosyntheticallyactive light that reaches the plant after being reflected by thearticle. For example, the article is placed “under a plant” or “around aplant” or in the “vicinity” of a plant or in the “proximity” of a plantwhen it is placed within, for example, 20 meters, 10 meters, 5 meters, 1meter, 0.5 meter, 0.1 meter, or 0.01 meter of the plant, or a distancebetween any two of these values.

As used herein, the term “light that is photosynthetically active” ismeant to encompass wavelengths of light approximately between about400-750 nm.

As used herein, the term “light that is not photosynthetically active”is meant to encompass wavelengths of light that are roughly not betweenabout 400-750 nm. For example, light that is not photosyntheticallyactive generally includes light having wavelengths between about 300-400nm (near ultra violet, NUV, band), between about 750 nm-1400 nm (thenear infrared, NIR, band), and between about 1400-3000 nm (short-waveinfrared, SWIR, band). In some embodiments, the reflective materialsdescribed herein convert light that is not photosynthetically activeinto light that is photosynthetically active. For example, light havingwavelengths between 300-400 nm, that is not photosynthetically active,can be at least partially absorbed by the reflective materials describedherein, and light having wavelengths between 400-750 nm, that isphotosynthetically active, may be subsequently fluoresced by thereflective materials described herein.

As used herein, the term “black body radiation” represents the upperlimit to the amount of thermally induced radiation that a material mayemit at a given temperature.

As used herein, a basic type of interaction between radiation (light)and matter is described by a photon transferring all of its energy to anatom or molecule. The energy of the photon raises an electron to ahigher energy level or, in the case of a molecule, raises the moleculeto a higher rotational or vibrational state. This increase in energystate of an atom or molecule may be reversed through scattering,emission, fluorescence or phosphorescence. For purposes herein, amolecule that has absorbed the energy of a photon is referred to as an“activated” molecule.

As used herein, the term “emit” is a measure of how strongly a bodyradiates at a given wavelength. One way to describe emission is as amechanism by which molecular kinetic energy (thermal energy) may beconverted into photons. Molecules may be activated by collisions witheach other and the released energy emitted as photons.

As used herein, the term “absorb” refers to the light-absorbing featuresof the reflective layers and reflective materials described herein. The“absorption coefficient” of the reflective layers and reflectivematerials described herein determine how far light of a particularwavelength may penetrate into these reflective layers and reflectivematerials before being absorbed. For example, in reflective layers andreflective materials with a low absorption coefficient, light is poorlyabsorbed. The absorption coefficient depends on the composition of thereflective layers and reflective materials, and on the wavelength oflight which is being absorbed.

As used herein, for a body in thermodynamic equilibrium, the amount ofthermal energy emitted equals the energy absorbed.

As used herein, the term “scatter” refers to light that has beenredirected and which exhibits diminished amplitude or intensity. Adissipation coefficient describes extent to which the amplitude orintensity of light diminishes, by scattering, upon the transmission oflight through a given thickness of a scattering medium (e.g., fog). Insome embodiments, scattering describes the mechanism for energy releasein which the molecule may spontaneously transition back to its originalstate by emitting a photon identical to that absorbed; the photonremains part of the radiation field but its direction of propagation isdiffused. In some embodiments, scattering describes the mechanism ofdiffuse reflection.

As used herein, the term “reflect,” refers to light that has beenredirected without a change in frequency. A reflection coefficientdescribes either the amplitude or the intensity of a reflected waverelative to an incident wave, and quantifies the proportion of energythat is reflected. Specular reflection is scattering in which thephoton's direction of propagation is changed, but not diffused. For manysurfaces, specularly reflected photons have an outgoing angle relativeto the local perpendicular, which is equal to the incident angle.Examples of good reflectors are polished metals; polished metals such asnickel, gold and aluminum are superior infrared reflectors.

As used herein, the term “retro-reflect,” refers to light that issubstantially redirected back to its source, such as the sun or anartificial light.

As used herein, the term “diffuse reflect,” refers to light that is, atleast partially, randomly redirected. In some embodiments, diffusereflected light includes some fraction of specularly reflected light orof retro-reflected light. In other embodiments, diffuse reflected lightexcludes retro-reflected light.

As used herein, a “metamaterial” generally features subwavelengthelements, i.e., structural elements with portions having electromagneticlength scales smaller than an operating wavelength of the metamaterial,and the subwavelength elements have a collective response toelectromagnetic radiation that corresponds to an effective continuousmedium response, characterized by an effective permittivity, aneffective permeability, an effective magnetoelectric coefficient, or anycombination thereof.

Some exemplary metamaterials are described by J. A. Bowers et al., inpublished U.S. patent application No. 20120019892; R. A. Hyde et al.,“Variable metamaterial apparatus,” U.S. patent application Ser. No.11/355,493; D. Smith et al., “Metamaterials,” International ApplicationNo. PCT/US2005/026052; D. Smith et al., “Metamaterials and negativerefractive index,” Science 305, 788 (2004); D. Smith et al., “Indefinitematerials,” U.S. patent application Ser. No. 10/525,191; C. Caloz and T.Itoh, Electromagnetic Metamaterials: Transmission Line Theory andMicrowave Applications, Wiley-Interscience, 2006; N. Engheta and R. W.Ziolkowski, eds., Metamaterials: Physics and Engineering Explorations,Wiley-Interscience, 2006; and A. K. Sarychev and V. M. Shalaev,Electrodynamics of Metamaterials, World Scientific, 2007.

In some embodiments a metamaterial may include a layered structure. Inthis sense, the “layers” of a metamaterial are distinct from the“layers” of an article. As such, a multilayered metamaterial may beincluded within one or more layers of an article. For example,embodiments may provide a metamaterial having a succession of adjacentlayers, where the layers have a corresponding succession of materialproperties that include electromagnetic properties (such as permittivityand/or permeability). The succession of adjacent layers may be analternating or repeating succession of adjacent layers, e.g., a stack oflayers of a first type interleaved with layers of a second type, or astack that repeats a sequence of three or more types of layers. When thelayers are sufficiently thin (e.g., having thicknesses smaller than anoperating wavelength of the metamaterial), the layered metamaterialstructure may be characterized as an effective continuous medium havingeffective constitutive parameters that relate to the electromagneticproperties of the individual metamaterial layers.

Additional metamaterials having a positive permittivity include but arenot limited to: semiconductors (e.g., at frequencies higher than aplasma frequency of the semiconductor) and insulators such as dielectriccrystals (e.g., silicon oxide, aluminum oxide, calcium fluoride,magnesium fluoride), glasses, ceramics, and polymers (e.g., photoresist,PMMA). In some embodiments a positive permittivity material is a gainmedium. Examples of gain media include semiconductor laser materials(e.g., GaN, AlGaAs), doped insulator laser materials (e.g., rare-earthdoped crystals, glasses, or ceramics), and Raman gain materials.Materials having a negative permeability include but are not limited to:ferrites, magnetic garnets or spinels, artificial ferrites, and otherferromagnetic or ferrimagnetic. Materials having a negative permittivityinclude but are not limited to: metals (e.g., at frequencies less than aplasma frequency of the metal) including the noble metals (Cu, Au, Ag);semiconductors (e.g., at frequencies less than a plasma frequency of thesemiconductor); and polar crystals (e.g., SiC, LiTaO₃, LiF, ZnSe) atfrequencies within a restrahlen band of the polar crystal (G. Schvets,“Photonic approach to making a material with a negative index ofrefraction,” Phys. Rev. B 67, 035109 (2003) and T. Tauber et al.,“Near-field microscopy through a SiC superlens,” Science 313, 1595(2006).

As used herein, the terms “liquid crystal” and “liquid crystallineparticle” are meant to describe a state of matter that has someproperties of a conventional liquid and others of a solid crystal. Forinstance, a liquid crystal may flow like a liquid, but its molecules maybe oriented in a crystal-like way. Liquid crystals include thermotropicand lyotropic liquid crystals. Thermotropic liquid crystals exhibit aphase transition, at a “phase transition temperature” or within a “phasetransition temperature range,” into a liquid crystal phase. Lyotropicliquid crystals exhibit phase transitions as a function of bothtemperature and concentration of the liquid crystals relative to asubstrate.

In some embodiments, liquid crystals include thermochromic compounds ormaterials that reversibly change color due to a change in temperature.In some embodiments, the reflective article includes leuco dyes orthermochromic compounds or materials that reversibly change color due toa change in temperature. Typically, thermochromic materials display areversible change of color at a specific temperature. Classes ofthermochromic materials include cholesteryl nonanoate andcyanobiphenyls. In some embodiments, the compositions and materialsdescribed herein can include a thermochromic material in an amount ofabout 0.01 wt. % to about 1 wt. %, about 1 wt. % to about 5 wt. %, about5 wt. % to about 10 wt. %, about 10 wt. % to about 25 wt. %, or a rangebetween and including any two of these values.

As used herein, the terms “photochromic” or “photochromic dye” are meantto describe compounds and materials that exhibit photochromism, which isthe reversible transformation of a chemical species between two forms bythe absorption of electromagnetic radiation, where the two forms havedifferent absorption spectra. Typically, photochromic dyes display areversible change of color upon exposure to light, as exemplified below.

Classes of photochromic dyes include the spiropyrans, spirooxazines(e.g., leuco dye), diarylethenes (e.g., stilbene, dithienylethenes, asshown above), azobenzenes, photochromic quinones (e.g.,phenoxynaphthacene quinone), and silver salts (e.g., silver chloride).The time required for a photochromic dye to complete its reversibletransformation from a first chemical species to a second chemicalspecies and back to the first chemical species is referred to as the“switch-back time.” In some embodiments, the photochromic dye undergoesa permanent color (e.g., photo-reactive or photo-changeable) change uponexposure to ultraviolet or visible light radiation.

The amount of light absorbed by the photochromic dye can be referred toas the quantum yield of the photochromic dye. In some embodiments, thequantum yield of the dye will be fixed. In some embodiments, the quantumyield of the dye will vary depending upon environmental conditions. Insome embodiments, the photochromic dye can revert between thermodynamicforms or isomers under certain conditions. Exemplary photochromic dyesare described in the published U.S. Patent Application No. 20050066453.

As noted, the present technology relates generally to a reflectivearticle for reflecting photosynthetically active bands of sunlighttowards one or more plants, and methods for growing plants where themethod includes placing the reflective article under, around, or in theproximity of the plant.

In some embodiments, the reflective article reflects light that is notphotosynthetically active with a reflection coefficient that increasesas the temperature of the reflective layers and reflective materialsincreases or the quantity of incident light increases. The reflectioncoefficient can be calculated from methods and according to equationsthat are known in the art. For example, the reflective article mayreflect sunlight that is not photosynthetcally active with a reflectioncoefficient that increases from about 5% to about 10%, from about 10% toabout 25%, from about 25% to about 50%, or a range between and includingany two of these values, as quantity of sunlight increases, for example,from morning until mid-day on clear day.

In some embodiments, the reflective article scatters incident light thatis not photosynthetically active with a dissipation coefficient thatincreases as the temperature of the reflective article increases or thequantity of incident light increases. The dissipation coefficient can becalculated from methods and according to equations that are known in theart. For example, the reflective article may scatter sunlight that isnot photosynthetically active with a dissipation coefficient thatincreases from about 5% to about 10%, from about 10% to about 25%, fromabout 25% to about 50%, or a range between and including any two ofthese values, as quantity of sunlight increases, for example, frommorning until mid-day on a clear day.

In some embodiments, the decrease or increase of optical properties ofthe reflective article occurs abruptly within a temperature range ofabout 5° C. or 2° C. In some embodiments, the decrease or increaseoccurs gradually within a temperature range of greater than about 10° C.In some embodiments, the decrease or increase occurs gradually within atemperature range of greater than about 5° C.

In some embodiments, a fraction of sunlight having a wavelength between300-400 nm, 750-1400 nm, or 1400-3000 nm is at least partially absorbed,reflected, or scattered by the reflective article at any giventemperature. In some embodiments, the fraction is about 5% to about 10%,about 10% to about 25%, about 25% to about 50%, about 50% to about 75%,about 75% to about 100%, or a range between and including any two ofthese values. In some embodiments, the temperature is about 20° C.,about 30° C., about 40° C., about 50° C., or a range between andincluding any two of these values. In some embodiments, at least 80% ofthe sunlight having wavelengths between 750 nm-1400 nm is at leastpartially absorbed, reflected, or scattered by the reflective layers andreflective materials at 27° C. In some embodiments, at least 80% of thesunlight having wavelengths between 1400-3000 nm is at least partiallyabsorbed, reflected, or scattered by the reflective layers andreflective materials at 27° C. In some embodiments, at least 80% of thesunlight having wavelengths between 300-400 nm is at least partiallyabsorbed, reflected, or scattered by the reflective article at 27° C.

In some embodiments, the reflective article described herein absorbslight that is not photosynthetically active and fluoresces light that isphotosynthetically active. In some embodiments, incident light havingwavelengths between 300-400 nm is at least partially absorbed by thereflective layers and reflective materials and light having wavelengthsbetween 400-750 nm is fluoresced by the reflective layers and reflectivematerials.

In some embodiments, optical downconversion is used to increase theefficiency of the reflective article described herein. Opticaldownconversion converts ultraviolet (UV) light into visible light, whichis used more efficiently by a solar cell. Similarly, UV lightdownconverted to visible light enhances photosynthetic activity in aphotosynthetic organism.

In some embodiments, optical upconversion is used to increase theefficiency of the reflective article described herein. Upconversion ofincoming radiation from the infrared spectrum into thephotosynthetically useful regime of the electromagnetic spectrum wouldbe very valuable; for example, a higher than average percentage ofincoming solar radiation is infrared light. In one embodiment, thereflective layers and reflective materials include lanthanide-dopedNaYF4 nanocrystals (NCs), used successfully in the upconversion of longwavelength radiation into the visible regime. (See Nanoscale (2010) Vol.2, Iss. 5, pp 771-7, The Royal Society of Chemistry.) Because thesenanoparticles have been shown to be readily dissolvable in water, it isforeseeable that such particles may be useful in the reflective articledescribed herein such as photosynthetically enhancing upconvertingreflective layers and reflective materials.

According to one aspect, the present technology provides a reflectivearticle including one or more diffuse reflecting materials and one ormore retro reflecting materials; where sunlight that isphotosynthetically active is at least partially diffuse reflected by thearticle and sunlight that is not photosynthetically active is at leastpartially retro reflected by the article. In some embodiments, thearticle is for placement under, around, or in the proximity of theplant. In some embodiments, sunlight that is photosynthetically activeis at least partially diffuse reflected towards leaves of a plant by thearticle, and sunlight that is not photosynthetically active is at leastpartially retro reflected away from the leaves of the plant by thearticle, when the article is in the vicinity of the plant. As such, atleast some of the sunlight that is not photosynthetically active isretro reflected back towards the sun, whereas at least some of thesunlight that is photosynthetically active is diffuse reflected towardsthe plant.

Thermal radiation is the emission of electromagnetic waves from matterthat has a temperature greater than absolute zero, and is themanifestation of the conversion of thermal energy into electromagneticradiation. The characteristics of thermal radiation will depend on theproperties of the surface it is emanating from, such as the surface'stemperature, spectral absorptivity and spectral emissive power. Thermalradiation is not monochromatic radiation but is composed of a continuousdispersion of photon energies, i.e., a characteristic radiativespectrum. In addition to the definition provided above for a black body,additionally, an ideal black body is characterized as a radiating bodyand surface in thermodynamic equilibrium, where the surface of the blackbody has perfect absorptivity at all wavelengths, and where such a bodyis defined to be a perfect emitter. Non-ideal black bodies emit lessthermal radiation at a given temperature than an ideal black body, andare generally characterized by an emissivity coefficient (multiplyingthe amount of radiation which would be emitted from an ideal black body)of between zero and one. A low emissivity material can be characterizedby an emissivity less than 0.75, less than 0.50, less than 0.25, or lessthan 0.10. A black body therefore (whether or not ideal) is an exampleof a body which is a thermal radiator and that has a radiative spectrum.

The total amount of radiation of all frequencies emitted by a body orsurface increases as a power of 4 when the temperature rises, e.g., itbehaves as a T⁴ function, where T is the absolute temperature of thebody. The rate of electromagnetic radiation emitted at a given frequencywill be proportional to the amount of absorption; for example, a surfacethat absorbs more red light will thermally radiate more red light. Thesecharacteristics will hold for the wavelength (color), direction,polarization and also coherence of the light wave. Therefore, thecharacter of the thermal radiation may be made to be polarized,coherent, and directional.

The emissivity of a material in general does not depend on itsthickness.

Most natural materials do not have thermal emissivities that correspondto a given visual emissivity (e.g., color of the object). The exceptionsare shiny metallic surfaces which possess low emissivities both in thevisible and far infrared. An example of this type of material is themulti-layer insulation that is used in spacecraft; such surfaces may beused to reduce heat transfer in both directions (incoming and outgoingradiation to a surface).

In some embodiments, the reflective article includes a low emissivityfilm, configured to reduce thermal radiation, e.g., to prevent excessivedrop in ground temperature during the night. In some embodiments, thereflective article is combined with a thermal insulator, which acts toreduce thermal conduction between the underlying ground and theoverlying air, reducing heat loss from convection and thermal radiation.The insulator may comprise a low conductivity material (e.g., foam orfibrous material), or may comprise multi-layer insulation (MLI).

An example of a low emissivity film is Solar Gard Silver Ag 25 Low-Efilm, which when used on windows will provide Summer/Winter insulation.It traps indoor heat from escaping through the film and prevents farinfrared radiation from entering a room through the film, transmitting22% of the visible light incoming and rejecting 77% of the solar energy.Films like these work by reflecting the infra-red component of solarenergy and absorbing the UV component. Typical absorptions for suchsilvered films are 65% for visible and infra-red light, and 99% for UV.A similar material layer would be useful in the reduction of heating ofsoil surrounding and covering roots of plants, trees and otherphotosynthetic organisms. A suitably designed low emissivity film layercould also be used to keep the ground warm during cold weatherconditions.

Such material might also be used to reduce water loss through groundevaporation. Likewise, condensation under the ground cover may bereduced by the use of an insulating film or similar material that limitsthe heat flow beneath the material layer, preventing the propagation ofmold, fungus or similar organisms that adversely affect plant growth.

In some embodiments, the reflective article consists of a single layer.In some embodiments, the reflective article includes two or more layers.In some embodiments, one layer comprises the diffuse reflecting materialand the retro reflecting materials. In some embodiments, one layercomprises the diffuse reflecting material, and another layer comprisesthe retro reflecting materials.

In some embodiments, each of the one or more layers further comprises apolymer. In some embodiments, the polymer is biodegradable. In someembodiments, the polymer is a naturally occurring biodegradable polymer(e.g., polysaccharide-based). In some embodiments, the polymer is asynthetic biodegradable polymer (e.g., such as those described inSynthetic Biodegradable Polymers: Advances in Polymer Science, Rieger,B.; Künkel, A.; Coates, G. W.; Reichardt, R.; Dinjus, E.; and Zevaco,Th. A. (Eds.) 2012, Vol. 245, Springer). In some embodiments, thepolymer is polyester, polyolefin, polyamide, polycarbonate, or acombination thereof.

Light transmissible polymeric materials may be used to produce thereflective articles (e.g., one or more of the layers of diffusereflecting material and/or retro reflecting material) described herein.In some embodiments, the polymeric materials can transmit at least 60,70, 80 or 90 percent of the intensity of the light incident upon it at agiven wavelength.

In some embodiments, the reflective article comprises a metal ormetallic material. In some embodiments, the metal is stainless steel oraluminum. In some embodiments, the reflective article comprisesaluminized Mylar®. In some embodiments the reflective article comprisesa foil or sheet. In some embodiments, the reflective article comprisesViagrow™ Lightite Diamond Reflective Mylar Film. In some embodiments,the reflective article comprises a double wavelength-reflectivemulti-layer film, such as that described in USPTO Patent Applications2013/0017382 and 2010/0132756. In some embodiments, the reflectivearticle comprises a Panda film. In some embodiments, the reflectivearticle comprises a GORE® Diffuse Reflector Product.

In some embodiments, the reflective article acts in the near-IR, visuallight, and UV. In some embodiments, the reflecting material is a diffusereflector.

In some embodiments of the article, reflection occurs primarily at thesurface of the reflective material. In some embodiments of the article,reflection occurs primarily by volumetric scattering throughout thereflective material.

In some embodiments, the reflective article may contain a crystal orcrystalline material. Such crystals or crystalline material may eitheroccur naturally in nature or be made synthetically. Examples are diamondand quartz.

In some embodiments, the crystalline material may be on the surface,embedded within, or beneath a layer of the reflective article. In suchembodiments, the layer may be an opaque, translucent or transparentmaterial.

In some embodiments, the reflective articles are made from one or morepolymers that are (a) relatively hard and rigid, (b) have a relativelylow elastic modulus for easy bending, curling, flexing, etc. or (c) acombination thereof.

For example, in some embodiments, the polymeric materials that are usedto make the corner-cube retro-reflector elements of the retro reflectingmaterial are relatively hard and rigid. The polymeric materials may be,for example, thermoplastic or crosslinkable resins. The elastic modulusof such polymers may be, e.g., greater than about 10×10⁸ or 13×10⁸pascals.

Examples of thermoplastic polymers that may be used to make thecorner-cube retro-reflector elements of the retro reflecting materialinclude acrylic polymers such as poly(methyl methacrylate);polycarbonates; cellulosics such as cellulose acetate, cellulose(acetate-co-butyrate), cellulose nitrate; epoxies; polyurethanes;polyesters such as poly(butylene terephthalate), poly(ethyleneterephthalate); fluoropolymers such as poly(chlorofluoroethylene),poly(vinylidene fluoride); polyvinyl halides such as poly(vinylchloride) or poly(vinylidene chloride); polyamides such aspoly(caprolactam), poly(amino caproic acid), poly(hexamethylenediamine-co-adipic acid), poly(amide-co-imide), and poly(ester-co-imide);polyetherketones; poly(etherimide); polyolefins such aspoly(methylpentene); poly(phenylene ether); poly(phenylene sulfide);poly(styrene) and poly(styrene) copolymers such aspoly(styrene-co-acrylonitrile),poly(styrene-co-acrylonitrile-co-butadiene); polysulfone; siliconemodified polymers (i.e., polymers that contain less than 10 weightpercent of silicone) such as silicone polyamide and siliconepolycarbonate; fluorine modified polymers such asperfluoropoly(ethyleneterephthalate); ethylenically unsaturatedcompounds and resins including styrene, divinylbenzene, vinyl toluene,N-vinyl pyrrolidone, N-vinyl caprolactam, monoallyl, polyallyl, andpolymethallyl esters such as diallyl phthalate and diallyl adipate, andamides of carboxylic acids such as and N,N-diallyladipamide;cationically polymerizable materials include but are not limited tomaterials containing epoxy and vinyl ether functional groups; andmixtures of the above polymers such as a poly(ester) and poly(carbonate)blend, a fluoropolymer and acrylic polymer blend.

Further examples of relatively hard and rigid thermoplastic polymersthat may be used to make the corner-cube retro-reflector elements of theretro reflecting material are listed in U.S. Pat. No. 5,840,405 to J. M.Shusta et al., “Glittering cube-corner retroreflective sheeting.”

In some embodiments, the portions and layers of the reflective articles,exclusive of the corner-cube retro-reflector elements, may be made fromany of the above-described polymers used to make the corner-cuberetro-reflector elements.

Additionally, in other embodiments, the portions and layers of thereflective articles, exclusive of the corner-cube retro-reflectorelements, may include a low elastic modulus polymer for easy bending,curling, flexing, conforming, or stretching, and for allowing thecorner-cube retro-reflector elements to become reoriented when thereflective article is exposed to heat and pressure. The elastic modulusmay be less than 5×10⁸ pascals, and may also be less than 5×10⁸ pascals.

Representative low elastic modulus polymers for optional use in one orlayers of the reflective article include: fluorinated polymers such as:poly(chlorotrifluoroethylene);poly(tetrafluoroethylene-co-hexafluoropropylene);poly(tetrafluoroethylene-co-perfluoro(alkyl)vinylether); andpoly(vinylidene fluoride-co-hexafluoropropylene); low densitypolyethylenes such as: low density polyethylene; linear low densitypolyethylene; and very low density polyethylene; plasticized vinylhalide polymers such as plasticized poly(vinyl chloride); polyethylenecopolymers including: acid functional polymers such aspoly(ethylene-co-acrylic acid) and poly(ethylene-co-methacrylic acid)poly(ethylene-co-maleic acid), and poly(ethylene-co-fumaric acid);acrylic functional polymers such as poly(ethylene-co-alkylacrylates)where the alkyl group is methyl, ethyl, propyl, butyl, andpoly(ethylene-co-vinylacetate); and aliphatic and aromaticpolyurethanes.

Further examples of low elastic modulus polymer that may be used to makethe reflective articles described herein are listed in U.S. Pat. No.5,840,405 to J. M. Shusta et al.

In some embodiments, the article, including the diffuse reflective orretro reflecting material, is permeable to gas transfer between theatmosphere and the ground.

The retro reflecting material and diffuse reflecting material can beseparately incorporated into the reflecting article (e.g., as retroreflecting materials or particles and diffuse reflecting materials orparticles within separate layers), or the retro reflecting material anddiffuse reflecting material can be co-integrated (e.g., as retroreflecting materials or particles and diffuse reflecting materials orparticles within the same layer), into the reflecting article (e.g., asingle-layer or multi-layered film, sheet, ground cover, billboard,screen, mesh, curtain, or a covering for a scaffold or pre-existingstructure such as the side of a building).

In some embodiments, the reflective article includes one or more layersof diffuse reflecting material; and one or more layers of retroreflecting material. In some embodiments, one layer of diffusereflecting material is mounted on top of one layer of retro reflectingmaterial. In some embodiments, one layer includes the diffuse reflectingmaterial and the retro reflecting material.

In some embodiments, the one or more diffuse reflecting materialsinclude a metamaterial, liquid crystal, photochromic material,thermochromic material, or a combination thereof.

In some embodiments, the one or more retro reflecting materials includea metamaterial, liquid crystal, photochromic material, thermochromicmaterial, or a combination thereof.

In some embodiments, the one or more retro reflecting materials comprisea photochromic material, a thermochromic material, a metal, or acombination thereof.

In some embodiments, the metamaterial comprises a semiconductor,insulator, glass, ceramic, or polymer. In some embodiments, themetamaterial comprises a layered structure. In some embodiments, thecompositions and materials described herein can include one or moremetamaterials in an amount of about 0.01 wt. % to about 1 wt. %, about 1wt. % to about 5 wt. %, about 5 wt. % to about 10 wt. %, about 10 wt. %to about 25 wt. %, about 25 wt. % to about 50 wt. %, or a range betweenand including any two of these values.

In some embodiments, the liquid crystalline particle comprises aliposome, apatone, and cholesteryl ester derivative (e.g., cholesterylnonanoate), cyanobiphenyl derivative, or a combination thereof. In someembodiments, the liquid crystalline particles are thermotropic. In someembodiments, the liquid crystalline particle has a phase transitiontemperature of about 0° C. to about 10° C., about 10° C. to about 20°C., about 20° C. to about 30° C., about 30° C. to about 40° C., about40° C. to about 50° C., or a range between and including any two ofthese values. In some embodiments, the liquid crystalline particle has aphase transition temperature of about 20° C. to about 30° C. In someembodiments, the compositions and materials described herein can includeone or more liquid crystalline particles in an amount of about 0.01 wt.% to about 1 wt. %, about 1 wt. % to about 5 wt. %, about 5 wt. % toabout 10 wt. %, about 10 wt. % to about 25 wt. %, about 25 wt. % toabout 50 wt. %, or a range between and including any two of thesevalues.

In some embodiments, the photochromic dye comprises, for example, aspiropyran, spirooxazine, triarylmethane, diarylethene, azobenzene,silver salt, stilbene, azastilbene, nitrone, fulgide, naphthopyran(e.g., 2H-naphthopyran or 3H-naphthopyran), quinone, anthrocyanin, or acombination thereof. In some embodiments, the photochromic dye has aswitch-back time of about 10 to about 500 seconds, about 500 to about1,000 seconds, about 1,000 to about 5,000 seconds, or a range betweenand including any two of these values. In some embodiments, thephotochromic dye has a switch-back time of about 500 to about 1,500seconds. In some embodiments, the photochromic dye has a switch-backtime of about 900 to about 1,100 seconds. In some embodiments, thecompositions and materials described herein can include one or morephotochromic dyes in an amount of about 0.01 wt. % to about 1 wt. %,about 1 wt. % to about 5 wt. %, about 5 wt. % to about 10 wt. %, about10 wt. % to about 25 wt. %, about 25 wt. % to about 50 wt. %, or a rangebetween and including any two of these values.

In some embodiments, the retro reflecting material comprises a metal. Insome embodiments, the metal is stainless steel or aluminum. In someembodiments, the retro reflecting material comprises aluminized Mylar®.In some embodiments the retroreflective material is a foil.

In some embodiments, any of the reflective articles described herein mayinclude a retro reflecting material that, itself, includes corner-cuberetro-reflectors (e.g., cube-shaped corners). In some embodiments, thecorner-cube retro-reflectors are about 0.001 cm to about 0.1 cm wide. Insome embodiments, the corner-cube retro-reflectors are about 0.01 cmwide. In some embodiments, the retro reflecting material comprises ametal. In some embodiments, the metal is stainless steel or aluminum. Insome embodiments, the retro reflecting material comprises aluminizedMylar®. In some embodiments, the retro reflecting materialretro-reflects sunlight with an efficiency that is greater when the sunis at its zenith in the sky than when the sun is not at its zenith onthe same day. In some embodiments, the retro reflecting materialretro-reflects sunlight with an efficiency that is at least 10% greaterat noon than its efficiency at 9 am or 3 pm on the same day.

In some embodiments, the efficiency with which sunlight is retroreflected by the article increases with at least one of: the temperatureof the article and the quantity of sunlight that contacts the article.

In some embodiments, the reflective article retro reflects sunlight thatis not photosynthetically active with a retro reflection coefficientthat increases as the temperature of the reflective article increases orthe quantity of sunlight increases. The retro reflection coefficient canbe calculated from methods and according to equations that are known inthe art. For example, the reflective article may retro reflect sunlightthat is not photosynthetically active with a reflection coefficient thatincreases from about 0% to about 5%, from about 5% to about 10%, fromabout 10% to about 25%, from about 25% to about 50%, from about 50% toabout 75%, from about 75% to about 100%, or a range between andincluding any two of these values, as quantity of sunlight increases,for example, from morning until mid-day on clear day.

In further embodiments, the reflective article absorbs sunlight that isnot photosynthetically active with an absorption coefficient thatincreases as the temperature of the reflective article increases or thequantity of sunlight increases. The absorption coefficient can becalculated from methods and according to equations that are known in theart. For example, the reflective article may absorb sunlight that is notphotosynthetically active with an absorption coefficient that increasesfrom about 0% to about 5%, from about 5% to about 10%, from about 10% toabout 25%, from about 25% to about 50%, from about 50% to about 75%,from about 75% to about 100%, or a range between and including any twoof these values, as quantity of sunlight increases, for example, frommorning until mid-day on clear day.

In some embodiments, the reflective article scatters sunlight that isnot photosynthetically active with a dissipation coefficient thatincreases as the temperature of the reflective article increases or thequantity of sunlight increases. The dissipation coefficient can becalculated from methods and according to equations that are known in theart. For example, the reflective article may scatter sunlight that isnot photosynthetically active with a dissipation coefficient thatincreases from about 0% to about 5%, from about 5% to about 10%, fromabout 10% to about 25%, from about 25% to about 50%, from about 50% toabout 75%, from about 75% to about 100%, or a range between andincluding any two of these values, as quantity of sunlight increases,for example, from morning until mid-day on clear day.

In some embodiments, the decrease or increase occurs abruptly within atemperature range of about 10° C., about 5° C., or about 2° C. In someembodiments, the decrease or increase occurs gradually within atemperature range of greater than about 10° C., or within a temperaturerange of greater than about 5° C.

In some embodiments, the sunlight that is diffuse reflected has an angleof reflection from about 1 to about 179 degrees, from about 1 to about160 degrees, from about 1 to about 120 degrees, from about 1 to about 90degrees, from about 1 to about 60 degrees, from about 1 to about 45degrees, from about 1 to about 30 degrees, from about 1 to about 15degrees, from about 1 to about 5 degrees, or a range between andincluding any two of these values, relative to the angle of incidence ofthe sunlight.

In some embodiments, sunlight having wavelengths between 400-750 nm, ora combination thereof, is substantially diffuse reflected by thereflective article; and sunlight having wavelengths that are not between400-750 nm is at least partially retro reflected by the reflectivearticle.

In some embodiments, the diffuse reflecting material comprises diffusereflecting particles having a diameter of less than about 100 μm. Insome embodiments, the diffuse reflecting material comprises diffusereflecting particles having a diameter of less than about 1 μm. In someembodiments, the diffuse reflecting particles are thermochromic. In someembodiments, the diffuse reflecting particles further comprise plasticor SiO₂.

In some embodiments, a fraction of sunlight having a wavelength of400-750 nm is substantially diffuse reflected by the reflective articleat any given temperature. In some embodiments, the fraction is fromabout 5% to about 25%, about 25% to about 50%, about 50% to about 75%,about 75% to about 100%, or a range between and including any two ofthese values. In some embodiments, the temperature is about 20° C.,about 30° C., about 40° C., about 50° C. or a range between andincluding any two of these values. In some embodiments, at least 80% ofthe sunlight having wavelengths between 400-750 nm, or a combinationthereof, is substantially diffuse reflected by the reflective article at27° C.

In some embodiments, a fraction of sunlight having a wavelength between300-400 nm, 750-1400 nm, or 1400-3000 nm is at least partially retroreflected by the reflective article at any given temperature. In someembodiments, the fraction is from about 25% to about 50%, about 50% toabout 75%, about 75% to about 100%, or a range between and including anytwo of these values. In some embodiments, the temperature is about 20°C., about 30° C., about 40° C., about 50° C., or a range between andincluding any two of these values. In some embodiments, at least 80% ofthe sunlight having wavelengths between 750 nm-1400 nm is at leastpartially retro reflected by the reflective article at 27° C. In someembodiments, at least 80% of the sunlight having wavelengths between1400-3000 nm is at least partially retro reflected by the reflectivearticle at 27° C. In some embodiments, at least 80% of the sunlighthaving wavelengths between 300-400 nm is at least partially retroreflected by the reflective article at 27° C.

As noted above, the term “retro-reflectors,” as used herein, includedevices that operate by returning light back to the light source alongthe same light direction with a minimum of scattering. For example, anelectromagnetic wave front is reflected by a retroreflector back along avector parallel to but opposite in direction from the incident wave'ssource. The retroreflector's angle of incidence is greater than zero.This is dissimilar to a planar mirror, which does this only if themirror is exactly perpendicular to the wave front, having a zero angleof incidence.

In some embodiments, the reflective articles described herein include aretro-reflective material such as a film or sheeting that has agenerally planar front surface and an array of prismatic corner-cuberetro-reflective elements protruding from a layer or the back surface ofthe film or sheet, such as those shown in FIGS. 1B and 2B.

In some embodiments, the reflective articles comprise microprismaticelements. In some embodiments, the retro reflective elements includecorner cube reflectors.

In a corner cube retro reflector, three mutually perpendicularreflective surfaces, are emplaced to form the corner of a cube. Thethree corresponding normal vectors of the corner's sides form a basis(x, y, z) that represent the direction of an arbitrary incoming lightray, [a, b, c]. When the ray reflects from the first side, x, the ray'sx component, a, is reversed to −a while the y and z components remainunchanged. As the ray reflects first from side x then from side y andfinally from side z the ray direction goes from [a, b, c] to [−a, b, c]to [−a, −b, c] to [−a, −b, −c]. It leaves the corner with all threecomponents [a, b, c] exactly reversed.

Corner reflectors occur in two varieties. In the first case, the corneris literally the truncated corner of a cube of transparent material suchas conventional optical glass (FIG. 4A). In this type of structure, thereflection is achieved by total internal reflection or by silvering ofthe outer cube surfaces. The second form of a corner reflector simplyuses mutually perpendicular flat mirrors bracketing an air space. Bothtypes have similar optical properties.

Large relatively thin retro reflectors may be formed by combining manysmall corner reflectors, using the standard optimal packing of the planewith congruent triangles.

Another form of retro reflector is used to reflect light from road signsand roadways into a driver's eyes rather than back into a car'sheadlights (FIG. 4B). This type of retro reflector consists ofrefracting optical elements with a reflective surface, so that the focalsurface of the refractive element coincides with the reflective surface,typically a transparent sphere and a spherical mirror. This effect canalso be optimally achieved with a single transparent sphere where therefractive index of the material is exactly two times the refractiveindex of the medium from which the radiation is incident. In the lattercase, the sphere surface behaves like a concave spherical mirror withthe required curvature for retro reflection. The refractive index doesnot need to be twice the ambient if it is greater than 1.5 times ashigh; there exists a radius from the centerline due to sphericalaberration at which incident rays are focused at the center rear surfaceof the sphere.

Such a retroreflector may consist of many small versions of thesestructures incorporated into a thin sheet or in paint. In the case ofglass beads in paint, the paint glues the beads to the surface whereretroreflection is required. The beads protrude as their diameter ischosen to be about twice the thickness of the paint.

A third and less common way of producing a retroreflector is to use thenonlinear optical phenomenon called phase conjugation. This techniquemay be used in advanced optical systems such as high-power lasers andoptical transmission lines, Phase-conjugate mirrors require acomparatively expensive and complex apparatus, as well as largequantities of power (as nonlinear optical processes can be efficientonly at high enough intensities). Phase-conjugate mirrors have aninherently much greater accuracy in the direction of the retroreflection, which in passive elements is limited by the mechanicalaccuracy of the construction.

In a non-limiting embodiment, the retroreflector may be a cornerreflector. In some embodiments, the corner reflectors are suitable forsending the light back to the source over long distances.

In some embodiments, the reflective articles described herein include aretro-reflective material such as a film or sheeting that includesprismatic corner-cube retro-reflecting elements such as those used insigning applications, including signing for traffic control. Exemplaryretro-reflective materials, such as films or sheetings are described,e.g., in U.S. Pat. No. 4,703,999 to G. M. Benson, “Wide-angle-reflectivecube-corner retroreflective sheeting;” published U.S. patent applicationNo.: US 2010/0195205 to H. D. Kim, “Cube-corner type self-reflectionsheet having improved tensile strength;” published European Patent App.No.: EP 2431774 to K. Amemiya et al., “Hexagonal corner cuberetroreflective article;” U.S. Pat. No. 6,114,009 to K. L. Smith et al.,“Asymmetric retroreflective cube corner sheeting mold and sheetingformed therefrom;” U.S. Pat. No. 6,390,629 to I. Mimura et al.,“Triangular-pyramidal cube-corner retroreflection sheet;” PublishedInternational PCT Application No.: WO1995/011464A2 to A. C. Bacon etal., “Ultra-flexible retroreflective cube corner composite sheetings andmethods of manufacture;” and U.S. Pat. No. 5,840,405 to J. M. Shusta etal., “Glittering cube-corner retroreflective sheeting.”

In use, the reflective article and, in particular, the retroreflectivematerial of the reflective article, is arranged with the front surfacedisposed generally toward the anticipated location of incident light.Light incident to the front surface enters the reflective article,passes through its single or multiple layers. According to certainembodiments, photosynthetically active light is diffuse reflected,whereas photosynthetically inactive light is retro reflected.

In one embodiment as shown in FIG. 1B, such as at mid-day when sunlightis most intense, nearly all of the light that is not photosyntheticallyactive is internally reflected by the faces of the cube-corner retroreflective elements so as to exit the front surface in a directionsubstantially toward the light source. This is referred to as retroreflection. The light rays are typically reflected at the cube faces dueeither to total internal reflection (TIR) from interfaces with anintentionally entrapped medium of greatly different refractive index,such as air, or to reflective coatings, such as vapor depositedaluminum.

In another embodiment as shown in FIG. 2B, during the early morning orlate afternoon when sunlight is less intense, some of the light that isnot photosynthetically active also diffuse reflected with thephotosynthetically-active wavelengths towards the leaves or a plant towarm the plant.

In some embodiments, the retro reflecting material includes corner-cuberetro-reflectors. In some embodiments, the corner-cube retro-reflectorsare about 0.001 cm to about 0.1 cm wide. In some embodiments, thecorner-cube retro-reflectors are about 0.01 cm wide.

In some embodiments, the reflective article includes diffuse reflectingparticles having a diameter of less than about 500 μm, about 100 μm,about 50 μm, about 10 μm, about 1 μm, or a range between and includingany two of these values. In some embodiments, the reflective articleincludes diffuse reflecting particles having a diameter of less thanabout 100 μm. In some embodiments, the reflective article includesdiffuse reflecting particles having diameters of about 755 nm-1405 nm,about 1405-3005 nm, or about 305-405 nm. In some embodiments, thediffuse reflecting particle sizes and diffuse reflecting particle sizedistributions, as used herein, can be measured with a MicromeriticsSedigraph 5100 Particle Size Analyzer. In some embodiments, the articlesdescribed herein are powdered, dissolved or suspended in a liquid, orpresented in a dry powdered state before doing a particle size analysis.X-ray scattered data can be recorded and converted to particle sizedistribution curves by one of ordinary skill in the art.

In some embodiments, the diffuse reflecting particles are thermochromic.In some embodiments, the diffuse reflecting particles include plastic orSiO₂. The plastic can include polypropylene, polyethylene, or other suchpolymers or co-polymers thereof.

In some embodiments, the density of the diffuse reflecting materialand/or the retro reflecting material is consistent throughout thereflective article. Thus, the article can be substantially homogenous.In other words, the diffuse reflecting material and/or the retroreflecting material can be consistently distributed throughout thereflective article.

In some embodiments, the density of the diffuse reflecting materialand/or the retro reflecting material is inconsistent throughout thereflective article. In other words, the diffuse reflecting materialand/or the retro reflecting material can be inconsistently distributedthroughout the reflective article. Thus, the article can also vary, forexample, by increasing the density of the diffuse reflecting material inareas of the article that are closest to the plant or areas which areexposed to maximum sunlight. Alternatively, the article can also vary,for example, by increasing the density of the diffuse reflectingmaterial in areas of the article that are relatively distant from theplant or areas which are exposed to minimum sunlight.

The reflective article can be incorporated into any device that can beplaced in the proximity of a plant. For example, in some embodiments,the reflective article is a ground cover. In some embodiments, thereflective article is a film, foil or a sheet, billboard, screen, mesh,curtain, or a covering for a scaffold or for a pre-existing structuresuch as the side of a building. In some embodiments, the reflectivearticle can be incorporated into a device that rotates or movesvertically and laterally.

In some embodiments, the reflective article is a ground cover. In someembodiments, the ground cover diffuse reflects sunlight that isphotosynthetically active towards the leaves of a plant, and retroreflects sunlight that is not photosynthetically active away from theleaves of the plant. In some embodiments, the plant yields soybean,corn, wheat, triticale, barley, oats, rye, rape, millet, rice,sunflower, cotton, sugar beets, pome fruit, stone fruit, citrus,bananas, strawberries, blueberries, almonds, grapes, mango, papaya,peanuts, potatoes, tomatoes, peppers, cucurbits, cucumbers, melons,watermelons, garlic, onions, carrots, cabbage, beans, peas, lentils,alfalfa, trefoil, flax, grass, lettuce, sugar cane, tea, tobacco orcoffee.

The article, such as a ground cover, may be rolled out in lengths ontothe ground between under, around or in the proximity of rows of trees inan orchard, for example, rows of vines in a vineyard, or rows of fruitsor vegetables to increase the amount of photosynthetically activesunlight to which the plants are exposed. In addition to reflectingphotosynthetically active sunlight, the article may also retainmoisture, suppress weeds, or warm soil. Each length of the article, suchas a ground cover, may be suitably secured in place such that it willnot be dislodged during wind or movement of traffic over the article.For example, a fastening system including a multiple number of prongfastening components may be fixed to the edges or side margins of thesheet material by pushing the prongs of the fastening components intothe material so that prongs pierce and pass through the material. Inturn the prongs may be fixed to adjacent trees, or alternatively stakesor pegs anchored into the soil. The article, such as a ground cover,will typically remain in place for some months, before being removed andoptionally reused in a subsequent growing season or on another crop inthe same growing season. Alternatively, the article, such as a groundcover, may be made from biodegradable materials and, thus, may besecured in place and allowed to gradually decompose.

The reflective article may be permeable to gas transfer between theatmosphere and the ground.

The reflective article may also include one or more agents whichstrengthen and/or improve the weather-resistance of the article. Forexample, such agents may include at least one light or heat stabilizerwhich will increase the resistance of the article to degradation throughexposure to solar radiation and temperature in an external environment,such as the following products, by BASF (Ludwigshafen, Germany), soldunder the following registered (®) trademarks: Irganox 245, Irganox 259,Irganox 565, Irganox 1010, Irganox 1035, Irganox 1076, Irganox 1098,Irganox 1135, Irganox 1141, Irganox 1330, Irganox 1425, Irganox 1520,Irganox 3052, Irganox 3114, Irganox 5057, Irganox MD 1024, Irgafos 168,Irgafos DDPP, Irgafos P-EPQ, Irgafos TNPP, Irgafos TPP, Irganox PS 800,Irganox PS 802, Irganox B 215, Irganox B 225, Irganox B 551, Irganox B561, Irganox B 612, Irganox B 900, Irganox B 921, Irganox B 1171,Irganox B 3557, Irganox B 3596, Irganox HP 3560, Irganox HP 2215,Irganox HP 2225, Irganox HP 2921, Ca 100, Chimassorb 119, Chimassorb944, Nor 371, Tinuvin 123, Tinuvin 144, Tinuvin 622, Tinuvin 765,Tinuvin 770, Tinuvin 783, Tinuvin 791, Chimassorb 81, Tinuvin 213,Tinuvin 234, Tinuvin 320, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin329, Tinuvin 350, Tinuvin 360, Tinuvin 492, Tinuvin 494, Tinuvin 571,Tinvin 622, Tinvin 765, Tinuvin 1577, Tinuvin P, Tinuvin B 75, Tinuvin B241, MD 1024, Araldite 7072, AO-I, Ni-Quencher, TiO₂ and CalciumStearate. Additionally or alternatively, the articles may include atleast one agent which increases the strength of the articles, such asthe addition of strength enhancing polymers such as polyester,polypropylene, high density polyethylene, or linear low densitypolyethylene.

Sheets and films comprising the reflective articles described herein maybe produced according to a number of known methods, including thosedisclosed in U.S. Pat. Nos. 5,450,235, 4,601,861, 4,486,363, 4,243,618,3,811,983, 3,689,346, 8,262,237, and 5,691,846.

In some embodiments, one or more of the reflective article(s) and theplant(s) are connected to a computer or a memory storage device. Thecomputer can be used, for example, to measure and monitor one or moreof, for example, the plant's rate of photosynthesis, the plant's rate ofgrowth, the amount of water that is consumed by the plant, or theplant's temperature, the time, air temperature, and the intensity ofsunlight. The computer can further be used, for example, to adjust thereflective article to increase or decrease the efficiency with whichsunlight that is not photosynthetically active is retro reflected by thereflective article. Non-limiting exemplary adjustments include rotatingthe reflective article or repositioning the reflective article by, forexample, moving the reflective article horizontally or vertically.Further non-limiting exemplary adjustments to the reflective articleinclude increasing or decreasing the efficiency of materials orcomponents within the reflecting article, such as the retro reflectingmaterial. Such adjustments can be used to increase or decrease theefficiency with which the sunlight that is not photosynthetically activeis at least partially retro reflected by the reflecting article.

In some embodiments, the plant is a tree, shrub, flower, grass, root,seed, landscape plant or an ornamental plant. In some embodiments, theplant yields a fruit, vegetable, or nut. In some embodiments, the plantis a tree, such as a fruit tree.

In some embodiments, the plant is selected from the group consisting ofa plant or tree that yields soybean, corn (maize), wheat, triticale,barley, oats, rye, rape, such as canola/oilseed rape, millet (sorghum),rice, sunflower, cotton, sugar beets, pome fruit, stone fruit, citrus,bananas, strawberries, blueberries, almonds, grapes, mango, papaya,peanuts, potatoes, tomatoes, peppers, cucurbits, cucumbers, melons,watermelons, garlic, onions, carrots, cabbage, beans, peas, lentils,alfalfa (lucerne), trefoil, clovers, flax, elephant grass (Miscanthus),grass, lettuce, sugar cane, tea, tobacco or coffee.

According to one aspect, the present technology provides a method forgrowing a plant, the method including placing a reflective articlebeside or beneath the plant, where the reflective article includes oneor more diffuse reflecting materials and one or more retro reflectingmaterials; where sunlight that is photosynthetically active is at leastpartially diffuse reflected, wavelength-dependently reflected, orretroreflectively reflected by the article and sunlight that is notphotosynthetically active is at least partially diffuse reflected,partially wavelength-dependently reflected, or partially retroreflectedby the article. In some embodiments, the method includes any of thereflective articles described herein. In some embodiments, when thearticle is under, around or in the proximity of a plant, sunlight thatis photosynthetically active is at least partially diffuse reflectedtowards leaves of a plant by the article and sunlight that is notphotosynthetically active is at least partially retro reflected awayfrom the leaves of the plant by the article.

In some embodiments, the method further includes measuring one or moreof the plant's rate of photosynthesis, the plant's rate of growth, theamount of water that is consumed by the plant, the type and rate ofgenerated gases such as oxygen, or the plant's temperature.

In some embodiments, the method further includes adjusting thereflective article to increase or decrease the efficiency with whichsunlight is reflected or retroreflected by the reflective article. Forexample, in some embodiments, the retro reflecting material is adjustedto retro-reflect sunlight with an efficiency that is greater when thesun is at its zenith in the sky than when the sun is not at its zenithon the same day.

In some embodiments, the plant's rate of photosynthesis is increased byabout 1% to about 5%, about 5% to about 10%, about 10% to about 20%,about 20% to about 30%, about 30% to about 40%, about 40% to about 60%,about 60% to about 80%, about 80% to at least about 100%, or a rangebetween and including any two of these values, after the placing step,during a period of time from about one day to about one week, from aboutone week to about one month, from about six months to about one year,from about one year to about five years, or a range between andincluding any two of these values.

In some embodiments, the plant's rate of growth is increased by about 1%to about 5%, about 5% to about 10%, about 10% to about 20%, about 20% toabout 30%, about 30% to about 40%, about 40% to about 60%, about 60% toabout 80%, about 80% to at least about 100%, or a range between andincluding any two of these values, after the placing step, during aperiod of time from about one day to about one week, from about one weekto about one month, from about six months to about one year, from aboutone year to about five years, or a range between and including any twoof these values.

In some embodiments, the amount of water consumed by the plant isreduced by about 1% to about 5%, about 5% to about 10%, about 10% toabout 20%, about 20% to about 30%, about 30% to about 40%, about 40% toabout 60%, about 60% to about 80%, or a range between and including anytwo of these values, after the placing step, during a period of timefrom about one day to about one week, from about one week to about onemonth, from about six months to about one year, from about one year toabout five years, or a range between and including any two of thesevalues.

In some embodiments, the plant's temperature is reduced by about 0° C.to about 1° C., about 1° C. to about 5° C., about 5° C. to about 10° C.,about 10° C. to about 20° C., or a range between and including any twoof these values, after the placing step, during a period of time fromabout one day to about one week, from about one week to about one month,from about six months to about one year, from about one year to aboutfive years, or a range between and including any two of these values.

In some embodiments, the plant's temperature is increased by about 0° C.to about 1° C., about 1° C. to about 5° C., about 5° C. to about 10° C.,about 10° C. to about 20° C., about 20° C. to about 30° C., or a rangebetween and including any two of these values, after the placing step,during a period of time from about one day to about one week, from aboutone week to about one month, from about six months to about one year,from about one year to about five years, or a range between andincluding any two of these values.

In some embodiments, the reflective article is used as a ground cover todecrease the thermal emissivity of the ground that it covers. As such,the reflective article can be used to retain heat within the ground thatsurrounds the roots of a plant. In some embodiments, the reflectivearticle decreases the thermal emissivity of the ground that it covers byabout 1% to 10%, about 10% to about 25%, about 25% to about 50%, about50% to about 75%, or about 75% to about 100%.

In some embodiments, the reflective article having a surface area isplaced above soil having a surface area such that a fraction of thesurface area of the soil is covered by the article and has a firsttemperature and a fraction of the surface area of the soil is uncoveredby the article and has a second temperature and the first temperatureexceeds the second temperature by at least about 1° C., 5° C., 10° C. or20° C. In some embodiments, the reflective article changes the albedo ofthe ground in the vicinity of the plant.

In one exemplary embodiment, the reflective article includes a sheetmade of a material which is smooth on its topside and irregular on itsbackside. The interface at the topside of the material is chosen to besubstantially reflective to light with photosynthetically inactivewavelengths (e.g., due to a coating on the reflective article or due tothe intrinsic properties of the reflective article), but substantiallytransparent to light with photosynthetically active wavelengths. Thematerial is pressed into a corrugated shape to form an array ofcorner-cubes. Because the topside of the reflective article is smooth,it exhibits specular reflection for light with photosyntheticallyinactive wavelengths; and because the reflective article is shaped intocorner-cubes, it exhibits retro-reflection. The reflective article istransparent to (at least) the photosynthetically active wavelengths,which pass through it towards the backside. The backside is reflective(e.g., due to a coating, or the material's intrinsic properties) at thephotosynthetically active wavelengths, so it can reflectphotosynthetically active light back through the topside of the articletoward the plant. This reflection is inherently retro-reflective due tothe corner-cube shape, but, because the backside of the reflectivearticle is irregular, the reflection is diffuse. The backsideirregularity can arise from thickness variations in the sheet formingthe reflective article, or it can arise from adhering small particles tothe backside of the reflective article.

The present technology, thus generally described, will be understoodmore readily by reference to the following Examples, which are providedby way of illustration and not intended to be limiting of the presenttechnology.

EXAMPLES Example 1

A non-limiting example of a reflective article as described herein, suchas a sheet, can be made as follows:

Step 1: The retro reflective layer. The retro reflective layer can bemade from a sheeting layer similar to that described, for example, inExample 1 of U.S. Pat. No. 5,691,846 to O. Benson Jr. et al.,“Ultra-flexible retroreflective cube corner composite sheetings andmethods of manufacture.”

Step 2: The diffuse-reflective layer. An additional layer made of adiffuse reflecting material can be prepared from one of the lighttransmissible polymeric materials described herein, such as low densitypolyethylene, having between 0.01 wt % and 90 wt %, e.g., 5 wt % of ametamaterial, liquid crystal, photochromic material, thermochromicmaterial or a combination thereof. The retro reflective layer anddiffuse-reflective layer may be fused or applied according to methodsknown to those of skill in the art of making multilayered plasticsheeting.

The reflective articles and sheeting described herein are designed toretro-reflect substantially all of the photosynthetically inactivelight, but diffuse reflect substantially all of the photosyntheticallyactive light. This combination of retro-reflective anddiffuse-reflective properties allows the reflective articles andsheeting described herein to be used as tools for enhancingphotosynthesis in plants and improving agricultural crop yield inorchards, agricultural fields.

Example 2 Use of the Reflective Ground Cover Sheets Described Herein toIncrease Crop Yields and Decrease the Volume of Water Used forIrrigation

(A) One hundred apple trees (“treated trees”) are surrounded withreflective ground cover sheets which are located as a ground coverunder, around, in the proximity of the trees, as described herein,during a growing season. One hundred apple trees of the same variety, inthe same orchard, are not surrounded with reflective ground cover sheetsas described herein (“control trees”). The apples from all two hundredtrees are harvested at the end of the growing season and the number ofapples harvested from the treated trees is compared to the number ofapples harvested from the control trees.

(B) Ten acres of corn (“treated corn field”) plants are surrounded withreflective ground cover sheets or grown up through reflective groundcover, as described herein, during a growing season. Ten acres of cornof the same variety, in an adjacent plot, are not surrounded withreflective ground cover sheets as described herein (“control cornfield”). The treated corn eventually grows to substantially overshadowthe reflective ground cover sheets. The corn from both fields isharvested at the end of the growing season and the amount of cornharvested from the treated corn field is compared with the amount ofcorn harvested from the control corn field.

EQUIVALENTS

The embodiments, illustratively described herein may suitably bepracticed in the absence of any element or elements, limitation orlimitations, not specifically disclosed herein. Thus, for example, theterms ‘comprising,’ ‘including,’ ‘containing,’ etc. shall be readexpansively and without limitation. Additionally, the terms andexpressions employed herein have been used as terms of description andnot of limitation, and there is no intention in the use of such termsand expressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the claimed technology.Additionally, the phrase ‘consisting essentially of’ will be understoodto include those elements specifically recited and those additionalelements that do not materially affect the basic and novelcharacteristics of the claimed technology. The phrase ‘consisting of’excludes any element not specified.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent reflectivearticles, apparatuses, and methods within the scope of the disclosure,in addition to those enumerated herein, will be apparent to thoseskilled in the art from the foregoing descriptions. Such modificationsand variations are intended to fall within the scope of the appendedclaims. The present disclosure is to be limited only by the terms of theappended claims, along with the full scope of equivalents to which suchclaims are entitled. It is to be understood that this disclosure is notlimited to particular methods, reagents, compounds, reflective articlesor biological systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as ‘up to,’ ‘at least,’ ‘greater than,’ ‘less than,’ and the like,include the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

While certain embodiments have been illustrated and described, it shouldbe understood that changes and modifications can be made therein inaccordance with ordinary skill in the art without departing from thetechnology in its broader aspects as defined in the following claims.

1. A reflective article comprising: a reflecting material configured todiffusely reflect at least 80% of incident sunlight that isphotosynthetically active; and a retro-reflecting material configured toretro-reflect at least 80% of incident sunlight that isnon-photosynthetically active; wherein: sunlight that isphotosynthetically active corresponds to wavelengths from 400 nm to 750nm; and the article is configured for placement under, around, or in theproximity of a plant.
 2. (canceled)
 3. The reflective article of claim 1consisting of a single layer comprising the reflecting material and theretro-reflecting material.
 4. The reflective article of claim 1comprising two or more layers.
 5. (canceled)
 6. The reflective articleof claim 4, wherein at least one layer comprises the reflecting materialand at least another layer comprises the retro-reflecting material. 7.The reflective article of claim 1, wherein the retro-reflecting materialcomprises corner-cube retro-reflectors.
 8. The reflective article ofclaim 7, wherein the corner-cube retro-reflectors are about 0.005 cm toabout 0.1 cm wide. 9-10. (canceled)
 11. The reflective article of claim1, wherein the retro-reflecting material comprises a metal.
 12. Thereflective article of claim 11, wherein the metal is stainless steel oraluminum.
 13. (canceled)
 14. The reflective article of claim 1, whereinat least one of the materials comprises a low emissivity film.
 15. Thereflective article of claim 1, wherein the article comprises a thermalinsulator. 16-17. (canceled)
 18. The reflective article of claim 1,wherein the reflective article comprises a film, foil, or sheet. 19.(canceled)
 20. The reflective article of claim 1, wherein an efficiencywith which sunlight is retro-reflected by the retro-reflecting materialincreases with increasing temperature of the article or the quantity ofsunlight that contacts the article. 21-22. (canceled)
 23. The reflectivearticle of claim 1, wherein the sunlight that is diffusely reflected hasan angle of reflection between 1 and 90 degrees relative to the angle ofincidence of the sunlight. 24-28. (canceled)
 29. The reflective articleof claim 1 further comprising a spectrally transparent layer of materialhaving a substantially smooth top surface and a diffusely reflectivebottom surface, wherein the spectrally transparent layer of materialcomprises an array of concave indentations.
 30. The reflective articleof claim 29, wherein the substantially smooth top surface is at leastpartially specularly reflective of sunlight that is notphotosynthetically active.
 31. The reflective article of claim 29,wherein the spectrally transparent layer of material is at leastpartially transparent to sunlight that is photosynthetically active. 32.The reflective article of claim 29, wherein the diffusively reflectivebottom surface is at least partially reflective off sunlight that isphotosynthetically active.
 33. The reflective article of claim 29,wherein the spectrally transparent layer of material has an irregularthickness.
 34. The reflective article of claim 29, wherein the diffuselyreflective bottom surface comprises a rough surface.
 35. The reflectivearticle of claim 29, wherein the diffusely reflective bottom surfacecomprises reflective particles.
 36. The reflective article of claim 29,wherein the concave indentations are shaped such that the top surfaceforms corner-cube retro-reflectors.
 37. The reflective article of claim29, wherein the layer of material is disposed on a substrate, such thatthe substantially rough bottom surface comprises an interface betweenthe layer of material and the substrate. 38-41. (canceled)
 42. Thereflective article of claim 1, wherein the reflecting material isconsistently distributed throughout the reflective article.
 43. Thereflective article of claim 1, wherein the reflecting material isinconsistently distributed throughout the reflective article.
 44. Thereflective article of claim 1, wherein the reflective article is aground cover.
 45. The reflective article of claim 1, wherein thereflective article is configured to reduce a thermal emissivity of theground covered by the article. 46-47. (canceled)
 48. The reflectivearticle of claim 1, wherein the article is substantially permeable togas transfer between the atmosphere and the ground. 49-50. (canceled)51. The reflective article of claim 1, wherein one or more of thereflective article(s) and the plant(s) are connected to a computer or amemory storage device.
 52. A method for growing a plant comprisingplacing a reflective article under, around, or in the proximity of theplant, wherein the reflective article comprises a reflecting materialconfigured to diffusely reflect at least 80% of incident sunlight thatis photosynthetically active; and a retro-reflecting material configuredto retro-reflect at least 80% of incident sunlight that isnon-photosynthetically active; wherein: sunlight that isphotosynthetically active corresponds to wavelengths from 400 nm to 750nm. 53-57. (canceled)
 58. The method of claim 52, wherein an amount ofwater consumed by the plant is reduced by at least 10% after the articleis placed.
 59. (canceled)
 60. The method claim 52, wherein thereflective article is placed over ground and a thermal emissivity of theground is reduced by at least about 10%.